Performance of trellis-coded CPM with iterative demodulation and decoding

Abstract

Interleaved trellis-coded systems with full response continuous-phase modulation (CPM) are considered. Upper bounds on the bit-error rate performance are derived for coherent detection on the additive white Gaussian noise and flat Rayleigh fading channels by considering the trellis code, interleaver, and CPM modulator as a serially concatenated convolutional code. A coherent receiver that performs iterative demodulation and decoding is shown to provide good bit error performance. Finally, a noncoherent iterative receiver is proposed and is shown to perform close to the coherent iterative receiver. I. INTRODUCTION M ANY communication systems employ nonlinear power amplifiers and, hence, require a low peak-to-average power ratio for the modulated signal. Examples of such systems include satellite and mobile communications systems. Continuous-phase modulation (CPM) is a constant envelope modulation technique and, hence, a good choice for such systems. Trellis-coded modulation (TCM) is a technique that combines modulation and coding in order to achieve coding gains without sacrificing data rate or bandwidth. When TCM is combined with CPM, high power and bandwidth efficiency can be achieved. Convolutionally encoded CPM on additive white Gaussian noise (AWGN) channels has been considered by many researchers [1]-[3]. Upper bounds on the bit-error rate (BER) have been derived for such systems [1], [3]. A detailed analysis of the distance spectrum and BER has been considered in [4]. The design and analysis of trellis-coded CPM (TCCPM) schemes for AWGN channels has also been considered in [5]. However, none of the aforementioned work has considered the use of an interleaver between the trellis code and the CPM modulator for AWGN channels. Similarly, they have also ignored the effect of the recursive nature of CPM modulator in designing TCCPM schemes. The performance of TCCPM for fading channels has been evaluated in [6]-[9]. A fading channel typically exhibits correlation in time and, when the correlation is high, the channel Paper approved by A. Ahlen, the Editor for Modulation and Signal Design of the IEEE Communications Society.

Turbo-coded multi-alphabet binary CPM for concatenated continuous phase modulation

“…Fig. 7 also compares the simulation result of the proposed scheme with those published in [5], [8] and [10]. The scheme matter experts for publication in the IEEE GLOBECOM 2005 proceedings.…”

“…A common solution is to improve the power efficiency by using the serial concatenated scheme in Fig. 1; see, e.g., [5], [8]. If R o is the rate of the outer code, the rate of this scheme is R = R o log 2 M bits/symbol.…”

Turbo Synchronization for Serially Concatenated CPM

“…Within the loop, the A-SISO CPM demodulator acts not only as an inner decoder but also as a synchronizer. Typical of SCCPM iterative receivers [2], the soft information is exchanged iteratively between the A-SISO demodulator and a channel decoder. We expect that both timing and phase estimates as well as information decisions are further refined by this procedure.…”

“…The serial concatenation of a convolutional code, random interleaver and a CPM modulator yields a turbolike code, called serially concatenated CPM (SCCPM), which can achieve near-Shannon limit performance by performing iterative demodulation/decoding [2]. SCCPM systems operate at characteristically low signal-to-noise-ratios (SNRs), which makes synchronization a challenging task, especially on timevariant channels with high and random dynamics.…”

LDPC-CPM Scheme and Its Iterative Receiving for MIMO System

“…There are many researches such as [4]- [6] detecting based on iterative decoding algorithm of LDPC coded MIMO system performance theory and simulation analysis, and verifying the excellent performance of the system. So far, the linear modulation schemes have been investigated in many MIMO architectures; however, the constant envelope modulation formats such as CPM [7] are more suitable for implementation in wireless system due to their high power amplifiers. Indeed, it has been focused especially on that extend the advantage of CPM signals to MIMO system and show high data rates performance [8].…”